Chapter 27 Layer 2 Protocol Tunneling
GS2200-24 User’s Guide
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In the following example, if you enable L2PT for STP, you can have switches A, B,
C and D in the same spanning tree, even though switch A is not directly
connected to switches B, C and D. Topology change information can be
propagated throughout the service provider’s network.
To emulate a point-to-point topology between two customer switches at different
sites, such as A and B, you can enable protocol tunneling on edge switches 1 and
2 for PAgP (Port Aggregation Protocol), LACP or UDLD (UniDirectional Link
Detection).
Figure 135 L2PT Network Example
27.1.2.1 Layer 2 Protocol Tunneling Mode
Each port can have two layer 2 protocol tunneling modes, Access and Tunnel.
•The Access port is an ingress port on the service provider's edge device (1 or 2
in Figure 135 on page 252) and connected to a customer switch (A or B).
Incoming layer 2 protocol packets received on an access port are encapsulated
and forwarded to the tunnel ports.
•The Tunnel port is an egress port at the edge of the service provider's network
and connected to another service provider’s switch. Incoming encapsulated
layer 2 protocol packets received on a tunnel port are decapsulated and sent to
an access port.
1
2
A
B
Service Provider's
Network
C
D
STP
STP
STP
